The Physical Determinants of Polish Swirl Visibility

Charles Lloyd
Visual Performance, Inc.

Dennis Havlin
Ford Motor Company

Proceedings of the SME's Finishing 1999 Conference and Exposition, Cleveland, Ohio.


An analysis of the optical properties of polish swirl marks in paint suggested ten lighting and viewing parameters will affect defect visibility. This paper describes two designed experiments in which the effects of the first four variables on this list were isolated and measured: 1) Viewing angle, 2) Defect-light source angle, 3) Light source size, and 4) Light source blurring. Thirteen observers provided ratings of defect of visibility for 133 combinations of lighting and viewing parameters. Statistically reliable estimates of the effects of the four independent variables were obtained. These results provide objective guidance for the design of an effective inspection facility.